Speciation
Alfred Russel Wallace created pioneering work in speciation; however, additional evidence over time has led to our current understanding of the theory of The formation of new and distinct species in the course of evolution..
A A type of organism that is the basic unit of classification. Individuals of different species are not able to interbreed successfully. is a group of organisms able to interbreed and produce fertile offspring.
New species can arise as a result of the following things:
- genetic variation - each population has a wide range of Different forms of the same gene. that can control their characteristics
- The natural process whereby the best-adapted individuals survive longer, have more offspring and thereby spread their characteristics. Sometimes referred to as 'survival of the fittest'. - the alleles which help an Living entity, eg animals, plants or microorganisms. to survive are selected in each population
- speciation - the populations become extremely varied and successful interbreeding cannot happen anymore
New species can also arise as a result of isolation:
- two populations of a species can become geographically separated because of the environment
- isolation can prevent interbreeding and the combination of genes within a species
- different mutations can take place in the isolated groups and create different The visible characteristics of an organism which occur as a result of its genes. within a particular location
- over time species may evolve to be different to each other, and they will not be able to interbreed
The diagram illustrates what could happen to an animal population, which is separated into two isolated groups by a geographical feature, such as a mountain or river.
Charles Darwin described the speciation of finches after his studies of the birds on the Galapágos Islands, which are a group of islands roughly 1,000 km off the coast of Ecuador. Darwin noticed that the finches on the different islands were similar to each other.
However, Darwin's studies revealed that the finches had wide variations in their size, beaks and claws from island to island. The finches' beaks differed depending on the local food source. Darwin concluded that because the islands were distant from the mainland, the finches that had arrived there had changed over time.